Process of making paper



Aug, 7, 1945; \o. KREss r-:TAL

l PROCESS OF MAKING PAPER Filed May 8, 1941 Ik USAN AT'To RN Y Patented Aug. 7, ieee PRCESS F otto ess, aparezca, wn., and Frank zeiten and Robert K. Statuen, Mechanicville, N. Y., as signers to West Virginialulp and Paper @ompany, New York, N. Y

., a corporation of Dela1 Application May 8, i941, Serial No. 392,404

' 5i claims. (oise- 21) Our present invention relatesto the utilization of so called broke of one type of paper in the manufacture of other types. Speciflicaliy, it has to do with the utilization of the broke from the manufacture of calcium sulilte (CaSOe) filled paper in the manufacture of other types of paper, as for example, clay filled paper. Se called broke is the term applied to paper that is discarded during manufacture and consists of trim mings, edges, wrinked and imperfect papel', etc.; it amounts to several per cent. of the total output of the machine. It is re-used in the paper making operations by being repulped and added to the furnish of stock to the paper machine. In the manufacture of other papers the use of theI broke accumulated from the manufacture of calcium suliite paper, either alone or in admixture with brokefrom other sources, has resulted in excessive foaming on the paper machine.

After considerable study We have discovered that the excessive foaming resulting from the use of repulped calcium sulflte broke is due to the presence of finely divided calcium sulfate (CaSUt) derived by oxidation from the CaSOa in the paper from which all or part of the broke was formed. Calcium sulfate is a. well known filler for paper, and in its customary form is unobjectionable and even desirable. However, when newly formed under the conditions obtaining in the beater chest or machine chest or with- 1n an hour or so previous to entering these chests, the calciumA sulfate particle size is exceedingly small, which gives rise to foaming if stock containing even minute quantities of such very nnely divided calcium sulfate is run on a paper machine. On the other hand, when the particle size is sufliciently large, diillculty from foaming disappears. l

The origin of the flnely divided, i. e., colloidal,

calcium sulfate may b e explained as follows:

The CaSOa filled paper broke, when normally repulped, alone or with other paper broke, is not oxidized to any extent because the presence of the CaSO keeps the pH substantially above 5.0 at which the oxidation is found to be very slow. However, when this broke is prepared for or is added to the furnish of another type of paper in which at some stage or other the pH drops below a suiilcient quantity of very iinely divided calcium sulfate, i. e., of colloidal or extremely fine particle size, as to give rise to foaming. One reason that the low pl-i is encountered in the manufacture of a clay filled sheet or sheet having substantially no filler is, that when the sheet is sized, an acidic reagent, usually alum, is added, which reacts with the rosin added to form vthe necessary size.

It is therefore a principal object of our invention to overcome the objectionable foaming attendant upon the use of calcium suliite broke, either alone or inadmixture with broke from other papers in the manufacture of paper having other fillers, or papers substantially uniilled, without having to maintain a pH of substantially more than 5 in the engines, tanks, chests, ilow boxes, etc., through which the broke pulp or the paper making furnish may pass-a matter which would be extremely dii'licult or impracticable to carry out, at least when rosin size is used.

In carrying out our invention we make use of conditions resulting in the conversion of calcium suliite into calcium sulfate of suiilcient particle size as not to occasion the formation of foam. In the normal operation of beating the broke into` pulp, air required for oxidation of the CaSOa is necessarily beaten into the pulp erably in the range 80 F. and 150 F. Desirably,

after the broke has been converted into pulp and conveyed to the broke storage chest, it is further aerated there to complete oxidation, and before the formation of a new sheet of paper it is necessary that suiiicient time elapse in order that the particle size of the calcium sulfate may be permitted to build up to a point where foaming does not occur. Normally the amount of time elapsing during which the treated broke is in circuit leading up to the head box of the ma- 5 chine, which may amount to a period of hours,

5, as for example in the manufacture of clay filled 'cMHsoinJfor-Casoia-rnsoi When this oxidation occurs, as in the manufacture l.of a clay lled sheet, .the oxidation is sufficiently slow so as to result in the formation of is sucient to bring this about.

Our invention may be somewhat better understood by reference to the 'annexed drawing which shows diagrammatically a preferred mode of treatment of the calcium suli'lte broke in accordiance with our invention. Dry broke consisting of all or a portion of calcium sulte filled paper is conveyed to the breaker engine l0, which may be 'admitted to maintain the temperature in the range preferably from F. to 150".l F. Due to pulp which is continuously withdrawn through pipe II, passing by meansa of pump I2 to broke storage chest I4. Here the broke pulp preferably receives further aeration by air introduced through the pipe I5 leading into perforated coil I6. Obviously, either one or a plurality Aof broke storage chests may be employed as is best suited to existing facilities of the paper manufacturer. Under the conditions of acidity and high temperature the calcium suli'lte is oxidized by the atmospheric oxygen to calcium sulfate. The reaction is, as above stated, the formation of calcium bisulfite by the action of the acid or acid salt (alum), and then the oxidation of the'latter t0 calcium sulfate.

The treated pulp is then withdrawn as needed from the storage chest I4 through pipe I'I by means of pump I8, and passed to so called broke measuring beater 20, the principal purpose' of which is to aiord Aa proper measure ofthe pulp used. This beater communicates, through pipe 2l, with one or more beater chests 22. Also communicating with chest 22 through pipey 23` is beater 24 handling new stock. After the pulp has .been in the beater chest for the requisite time it is removed therefrom and, after having various operations normal to paper making practice per'- iormed upon it, is passed to the head box of the paper making machine, not shown.

It will be understcodthat the calcium sulilte, after oxidation to calcium sulfate, will be maintained in the stock system prior to flowing onto the wire of the paper making machine for a period of hours, as it is found that if the freshly formed calcium sulfate is added tothe furnish, foaming will result. If, however, the furnish consame in the form of pulp in the furnish to the paper making machina'in which the pH of the furnish falls to 5 or below, which consists in pulping said calcium sltebroke in the presence of air and under pH conditions of 5 or below to oxidize the calcium sulilte substantially completely to calcium sulfate, and introducing the so treated broke pulp into the machine after the calcium sulfate no longer causes objectionable foaming.

2. The method of utilizing calcium sulflte broke in the manufacture of paper, in which the pH of the furnish may'fall to 5 or below, which consists in pulping the broke', maintaining the pH of the broke pulp so formed below 5 while affording contact of the pulp 'with oxygen until substantially all the calcium sulite is oxidized to calcium sulfate, but withholding the so treated broke pulp from the machine until the formed calcium sulfate will no longer cause objectionable foaming, and then adding the pulped broke so withheld to Asaid furnish.

tained at from 4 to 4.5, and the temperature maintained at 80 to 150 F.

4. The method of utilizing calcium sulfite broke in the manufacture of paper by incorporating same in the form of pulp in the furnish to the .paper-making machine, which furnish does not contain any substantial q'uantity of calcium sulte as a illler, and in which the pH of the furnish falls to 5 or below, which consists in beating the.

said calcium sulilte broke intofpulp, passing the taining the freshly formed calcium sulfate is ai- ,lowed to stand for a period of hours, foaming is eliminated. Our explanation for this, as above pointed out, is that by standing, the particle size of the calcium sulfate is increased to the point where foaming no longer occurs.

It will be seen from the foregoing that our invention permits the use of calcium suliite broke in the manufacture of clay i'llled paper, for example, the same as if it 'were clay lled broke,

whereby segregation and storage of the calcium sulflte broke (requiring extra equipment and storage space) until such time as calcium sulte papers are again run,are eliminated.

While we have illustrated and described in detail certain preferred forms of our invention,

it is to be understood that changes may b e made broke pulp so formed to a chest, there aerating said broke pulp under pH conditions of 5 or below until oxidation of the calcium suliite. to calcium sulfate is substantially complete, but withholding such aerated broke pulp from said-machine until the formed calcium sulfate will no longer cause objectionable foaming.

5. 'I'he method of utilizing calcium sulfltebroke in the manufacture of paper by incorporating same in the form of pulp in the furnish to the paper making machine, which furnish does not contain any substantial quantity of calcium suiiite as a ller, and in which the pH of the furnish falls to 5 or below, which comprises the steps of beating the broke into pulp at a beating sta-v tion, temporarily storing the broke pulp in a chest at a storage station, and converting substantially all the calcium sulilte to calcium sulfate, the converting including aeration of said broke pulp under pH conditions of 5 or below at at least one of said stations, but withholding such aerated broke pulp from said machine until the formed calcium sulfate will no longer causeobjectionable foaming.

. O'I'IO KRESS.

FRANK ZEI'I'LIN. ROBERT K. STAMAN. 

